Stat5 Signaling Specifies Basal versus Stress Erythropoietic Responses through Distinct Binary and Graded Dynamic Modalities
Figure 8
Dimmer-switch model of Stat5 signaling.
(A) The operation of a dimmer switch combines binary and graded components. The closing of an “on/off” switch closes an electric circuit, allowing current to flow and switches on a dim light. A gradual further turning of the power-switch dial permits a gradual decrease of the circuit's resistance, with a consequent graded increase in the electric current and light intensity. (B) The p-Stat5 signal is turned “on” through a binary action, to produce a low-intensity but decisive signal in S3 erythroblasts or in EpoR-HM erythroblasts. In S1 early erythroblasts, this signal can increase further with a gradual further increase in Epo concentration. No further increase takes place in mature S3 erythroblasts, though the number of signaling erythroblasts increases with increasing Epo.